Study on proportion optimization and damage constitutive model of coal-based solid waste cemented backfill

FAN Donglin

doi:10.11799/ce202510017

Abstract：To reduce carbon emission through the resource utilization of coal-based solid wastes(e.g.,coal gangue)for Shendong Coal Group,a novel backfill grouting material was developed using calcined coal gangue powder and fly ash as partial substitutes for cement,with nano-silica added as an additive.The composition and microstructure of the raw materials were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Based on the response surface methodology(RSM)and Box-Behnken experimental design,the effects of various components on the uniaxial compressive strength and fluidity of the slurry were investigated,and an optimal mix proportion was determined.Meanwhile,a new damage constitutive model was established,which fully describes the stress-strain behavior,providing a reference for engineering applications.Experimental results show that the key factors influencing the fluidity of the grouting material follow the following order:fly ash replacement rate>calcined coal gangue powder replacement rate>nano-SiO2 addition rate;while the order of influence on the uniaxial compressive strength is:fly ash replacement rate>nano-SiO2 addition rate>calcined coal gangue powder replacement rate.The optimal ratios of the factors are as follows:calcined coal gangue powder replacement rate of cement 21.16%,fly ash replacement rate of cement 30.3%,and nano-SiO2 addition rate 0.511%.